1. Field of the Invention
This invention relates to annular separators for double walled pipe structures.
2. Description of Related Art
It has been proposed for transporting oil and/or gas from off-shore oil wells, to provide a pipeline formed of double walled pipes constructed from an outer and inner pipe of a generally coaxial disposition, the inner pipe being arranged to carry the oil or gas, which will usually be at an elevated temperature relative to ambient conditions, the inner and outer pipes being held apart by separators or bulkheads acting as seals between lengths of the annular space between the pipes, and the annular space between the inner pipe and the outer pipe being filled with hollow microspheres of alumino-silicate, for example, whereby thermally to insulate the oil or gas contained within the inner pipe, increase the strength of the structure and in certain circumstances enable the pipeline structure to float on the water surface. A pipeline formed of such inner and outer pipes can, with appropriate bulkheads between the two along their length, and interconnection to successive pipes by welding for example, act as a single compliant structure capable of being handled as a single pipe.
It has been proposed to use as such bulkheads an annular ring of rubber or similar resilient material of generally rectangular cross-section sandwiched between two supporting steel rings one on each side bolted together through the rubber.
One problem with such a structure is that when the pipeline is bent, such as when it is coiled on to a drum for carriage purposes, it deforms somewhat into an oval section, and the bulkheads can form distortions in the slightly oval bent or coiled pipe structure because of resistance to the oval deformation of the pipe structure.